ruby-on-rails – ruby??包括vs扩展

module CroppableImage
  def croppable_image(*image_names)
    image_names.each do |image_name|

      define_method "#{image_name}_sizes" do
        { :cropped => read_attribute("#{image_name}_size").to_s,:large => "800x800>" }
      end

      define_method "#{image_name}_geometry" do |style|
        style ||= :original
        @geometry ||= {}
        @geometry[style] ||= Paperclip::Geometry.from_file(eval "#{image_name}.path(style)")
      end

      define_method "#{image_name}_aspect_ratio" do
        width,height = read_attribute("#{image_name}_size").split("x")
        width.to_f / height.to_f
      end

      private

        define_method "reprocess_#{image_name}" do
          eval "#{image_name}.reprocess!"
        end

    end
  end

end

将这个包含在我的模型中,似乎我必须使用扩展.我认为扩展是包括类方法.我是从java的背景 – 我以为使用扩展基本上创建静态方法的类.

class Website < ActiveRecord::Base
  extend CroppableImage
  croppable_image :logo,:footer_image

– 这个工作

看来,我真正想要的是创建实例方法.

class Website < ActiveRecord::Base
  include CroppableImage
  croppable_image :logo,:footer_image

– 这引发了错误“undefined method`croppable_image’for#”

任何人都可以解释发生了什么,如果我应该在这种情况下使用包含或扩展.多谢你们